The present invention relates to diaphragms for use in industrial process instrumentation, and more particularly, to a diagnostic system for detecting rupture or thinning of diaphragms.
Many industrial instruments include a diaphragm element coupled to an industrial process for measuring a parameter of the process. For example, some pressure transmitters include an isolating diaphragm that is coupled to an industrial process. Pressure measurements may be taken directly from the diaphragm based on the diaphragms deflection in response to pressure or may be taken indirectly by a remote pressure sensor that is coupled to the isolating diaphragm by a fluid filled capillary. Rupture or thinning of the diaphragm can alter measurement readings, and/or permit process fluid to escape from the industrial process. Additionally, fill fluid from the fluid filled capillary may escape through a rupture in the isolating diaphragm to contaminate the process.
Conventionally, one technique for detecting rupture of the isolating diaphragm of a remote pressure sensor uses leads extending into the fluid fill. A measurement device coupled to the leads is adapted to detect a change in resistance between the two wires. If conductive process fluid flows through a rupture in the isolating diaphragm, the resistance between the leads changes, thereby indicating a rupture. Another technique is to monitor for an abrupt change in the transmitter measurement, which can indicate a rupture. However, these techniques only identify rupture of the diaphragm after the rupture has occurred, and potentially after fill fluid has leaked into the process.
There is an on-going need in the art for real-time detection of thinned or ruptured diaphragms. Embodiments of the present invention provide solutions to these problems and provide advantages over conventional diagnostic systems.